1. Field of the Invention
The present invention relates to a rechargeable battery, and in particular, to a battery module which is constructed by interconnecting a plurality of unit cells, and involves heightened cooling efficiency of the unit cells.
2. Description of Related Art
A conventional high-capacity rechargeable battery (referred to hereinafter as a “battery module”) is constructed by serially interconnecting a plurality of rechargeable battery cells (referred to simply as the “unit cells”). The respective unit cells include an electrode assembly with positive and negative electrode plates while interposing a separator, and a case mounting the electrode assembly therein. A cap assembly is fitted to the case to seal it, and positive and negative electrode terminals are electrically connected to current collectors of the positive and the negative electrode plates of the electrode assembly.
In typical prismatic batteries, the respective unit cells are arranged such that the positive and the negative electrode terminals thereof protrude out of the top of the cap assembly and alternate with the positive and negative electrode terminals of the neighboring unit cell. A conductor interconnects the screwed negative and positive electrode terminals via a nut.
If the temperature difference between the locations of the respective unit cells within the battery module is large, the battery capacity deteriorates, so heat dissipation is advantageous. If the heat is not dissipated properly, the temperature deviation between the respective unit cells deteriorates the charge/discharge efficiency. The internal temperature of the battery is elevated due to the heat generated from the unit cells to deteriorate the battery capacity, and, in a serious case, the battery may explode.
Particularly when the battery module is used to drive a motor for an electronic washer, an electric scooter or a vehicle (such as an electric vehicle or a hybrid electric vehicle), the module is charged and discharged by a high electric current so that the heat generated due to the internal reaction of the unit cells during the usage thereof is liable to be elevated to a considerable degree. This badly affects the battery characteristic, and deteriorates the inherent battery capacity. Accordingly, proper heat dissipation is advantageous.